In a wafer-level lens process in which a plurality of lenses is arranged in a plan direction of a wafer substrate, it is difficult to obtain the shape accuracy or the position accuracy when the lenses are formed. In particular, a high level may be demanded in a process in which wafer substrates are stacked to manufacture a stacked lens structure. It is difficult to stack three layers or more in mass production level.
Various techniques related to the wafer-level lens process have been devised and proposed. For example, Patent Literature 1 proposes a method in which when a lens material is filled into through-holes formed in a substrate to form a lens, the lens material itself is used as an adhesive to stack wafer substrates.